1. FIELD OF THE INVENTION
The present invention relates generally to tools used for cutting and machining, and more specifically to various embodiments of a tool or insert holder having an integral coolant passage therewith. The holder may be adapted for stationary machining of a moving workpiece (e. g., lathe work), or may be adapted for rotary machining of a relatively stationary workpiece (e. g., milling). The tool holder includes a replaceable cooling nozzle having a novel coolant passage therethrough, which provides essentially laminar flow of coolant therethrough and precludes significant expansion of the coolant stream after it leaves the nozzle outlet, thereby providing greater chip breaking force and a greater volume of fluid contact with the cutting insert and workpiece to provide greater heat transfer.
2. DESCRIPTION OF THE RELATED ART
It is well known in the art of machining and cutting material, particularly metal, that the provision of some form of fluid (e.g., a light cutting oil of some sort) greatly prolongs the life of the cutting bit or insert between sharpenings, and also greatly speeds the cutting or machining of the material, by reducing friction and assisting in heat transfer from the working edge of the tool.
Accordingly, the practice of using such cutting fluid has been known for many years, and various cutting tool holders adapted for use with powered machine tools also have provision for the attachment of passages and/or nozzles for delivering a stream of cutting fluid to the cutting edge of the tool or tool insert. However, most such tool holders rely on clamps or similar arrangements to secure the nozzle to the tool holder, which procedure can result in misalignment of the nozzle with the cutting edge of the cutting insert, resulting in relatively little cutting fluid reaching the most critical point where it is needed.
Even where the nozzle is aimed relatively precisely, the fluid flow generally breaks up and forms more of a spray, rather than a cohesive liquid stream, as is desired. This is primarily due to the turbulent flow through conventional nozzles in combination with the extremely high pressures often used to deliver such coolant fluid, along with the circumferential flow vector which accompanies the round interior cross sectional shape of conventional nozzles. The sudden pressure drop as the fluid leaves the nozzle, along with the centrifugal reaction of the fluid due to the circumferential flow vector, results in rapid breakup and expansion of the fluid stream. The resulting spray cannot deliver the force required to break up chips from the cutting or machining process, and cannot provide efficient heat transfer. To this point, the solution has been to use ever increasing volumes and pressures of fluid, in an attempt to get sufficient fluid to the cutting tool edge to provide the desired chip breaking and cutting edge cooling actions.
Accordingly, a need will be seen for a tool holder which includes an integrated coolant passage therewith, with replaceable coolant nozzles to allow the machine operator to change nozzles having different size orifices according to the needs of the specific job. The various nozzles have an axial flow which is automatically aligned with the cutting edge of the tool insert for optimum efficiency. The nozzles also include a novel interior passage shape to provide cohesive fluid flow for the coolant after it leaves the nozzle. The present tool holder may be adapted for stationary use against a rotating workpiece, as in a lathe, or may comprise a rotating tool holder for use against a relatively stationary workpiece, as in a milling machine. A discussion of the related art known to the present inventor, and its differences and distinctions from the present invention, is provided below.
U.S. Pat. No. 3,741,049 issued on Jun. 26, 1973 to George B. Anderson describes a Cutting Tool for use in machining operations. The tool actually comprises a cutting bit or insert holder which in turn comprises a tool cartridge, a tool block, and a filler block for locating the tool cartridge on the tool block. A coolant fluid passage is provided through the tool block, but the coolant nozzle is not connected directly to this passage. Rather, the nozzle extends from the filler block, which has a passage therethrough which communicates with the tool block coolant passage. In any case, Anderson does not disclose any particular internal passage shape for the nozzle outlet, and discloses an elbow directing flow radially from the filler block passage.
U.S. Pat. No. 4,848,198 issued on Jul. 18, 1989 to Harold J. Royal et al. describes a Chip Breaking Tool Holder including a cutting insert clamp and main tool holder body. The clamp and body each have a coolant passage therethrough, with the two passages communicating with one another. While the Royal et al. coolant passage succeeds in directing the fluid flow directly toward the cutting edge of the insert, the connection between the passages of the two components is complex and requires a sophisticated seal. Moreover, this assembly must be loosened each time a cutting insert is changed or repositioned in the holder, thus increasing the chances of leakage. Royal et al. do not disclose any particular cross sectional shape for the internal passage of their nozzle.
U.S. Pat. No. 5,272,945 issued on Dec. 28, 1993 to Thomas A. Lockard describes a Toolholder Assembly And Method, wherein the coolant nozzle comprises a threaded bolt having a hollow center and partially cross drilled head, thereby forming a passage through the bolt with a radial outlet. The bolt is threaded into a mating passage in the tool block. The threaded configuration of the assembly allows the coolant nozzle bolt to be turned to direct the coolant flow as desired, but also allows for the inadvertent misalignment of the flow with the cutting edge of the insert. The axial outlet of the present nozzle precludes any possibility of misalignment. Also, Lockard discloses only a circular internal cross section for his coolant nozzle passage, unlike the non-circular configuration of the present coolant passage nozzle outlet.
U.S. Pat. No. 5,340,242 issued on Aug. 23, 1994 to William D. Armbrust et al. describes a Chip-Breaking Toolholder With Adjustable Orifice Cap. The toolholder body includes a coolant passage therethrough, but the fluid is further routed through a separate block having a coolant nozzle outlet therein. A hollow bolt secures the coolant nozzle block to the toolholder body, with fluid passing through the bolt and radially outward from a lateral passage below the head of the bolt, which communicates with the coolant nozzle block. The result is a complex assembly, requiring a plurality of seals as well as including an additional eccentrically headed bolt acting as a cam for adjustment of the coolant passage block. FIG. 2 of the Armbrust et al. patent makes clear the problem of coolant stream breakup which is solved by the present invention, but Armbrust et al. do not disclose any particular outlet shape for their coolant nozzle to address this problem.
U.S. Pat. No. 5,346,335 issued on Sep. 13, 1994 to Jacob Harpaz et al. describes a Metal Cutting Tool having a cutting insert with a coolant passage extending therethrough. The coolant passage communicates with a fluid passage in the tool holder block. Harpaz et al. require a specialized cutting insert for use with their tool; the cutting insert would be costly to produce, due to the forming of the coolant passage through the hardened material of the insert. Moreover, Harpaz et al. are silent regarding any cooling passage internal shape other than circular for their cutting tool.
U.S. Pat. No. 5,402,696 issued on Apr. 4, 1995 to Gil Hecht et al. describes a Seal Insert For The Shaft For A Workpiece, comprising a threaded insert which fits between a threaded coolant duct nipple and the unthreaded end of a tool holder adaptor. The device acts as a connector between the coolant nipple and the adaptor in cases where the adaptor does not have a mating threaded end to fit the nipple (e. g., where the adaptor has been shortened by cutting off the threaded end). No disclosure is made of any coolant nozzle configuration or orientation, although Hecht et al. mention the coolant flowing from apertures "so as to be sprayed on to the work piece . . . " (column 3, lines 53-54). Thus, Hecht et al. recognize the problem of the coolant flow dissipating as a spray, rather than being concentrated as a cohesive stream, but offer no solution to the problem.
U.S. Pat. No. 5,439,327 issued on Aug. 8, 1995 to Raphael Wertheim describes a Metal Cutting Tool wherein the cutting insert holder includes at least one coolant passage which terminates at an external edge adjacent at least one face of the cutting insert. The inserts are specially formed with at least one external coolant channel formed between the coolant passage outlet of the tool holder and the working edge of the insert. The specially formed inserts are thus relatively difficult and costly to manufacture, as in the case of the inserts of the '335 patent to Harpaz et al (Wertheim being a co-inventor), discussed further above. No mention is made by Wertheim of any particular cross sectional shape of the interior of the coolant passage in the tool holder block.
British Patent Publication No. 795,729 published on May 28, 1958 describes Improvements In Cutting Tools For Lathes, comprising a cutting tip which is brazed or cemented to the tool insert, the insert in turn being bolted to the tool holder. The tool holder and insert are adapted to provide a jet of carbon dioxide (rather than a cooling oil or other liquid) terminating in a plurality of fine channels (rather than a single liquid outlet) "which are directed away from the cutting tip of the tool . . . " (page 2, column 1, lines 32-33) rather than toward the cutting tip. The disclosure also teaches the direction of the gas away from the chips being cut, in order to avoid cooling the chips. This teaches away from the present invention, in which the coolant is directed at the cutting tip of the insert, and thus at chips as they are being cut. The shock cooling action on the chips assists in breaking up the chips, which is considered desirable.
British Patent Publication No. 2,212,078 published on Jul. 19, 1989 describes a Cutting Tool With Cutting Fluid Channel disposed along the outer surface of the tool. This teaches away from the internal passage of the present tool holder, and cannot direct a stream of fluid under high pressure as provided by the present invention.
Finally, Soviet Patent Publication No. 1,230,799 published on May 15, 1986 illustrates a Water Cooling System For Tipped Lathe Tools wherein at least the tool block and insert holder include coolant passages therethrough. The insert holder includes a plurality of relatively small passages, to distribute the coolant over the face of the cutting insert. The assembly includes a compensating plate for retaining the coolant until it reaches a sufficiently high temperature to vaporize, whereupon the coolant flows from the outlets of the insert holder as steam. The liquid coolant used with the present invention is not heated to such a degree, as it is separated from the cutting tip before being ejected from the outlet nozzle extending from the tool block. As in the case of the related art discussed above, the Soviet patent makes no disclosure of other than circular or semicircular internal shapes for the coolant passages.
None of the above inventions and patents, either singly or in combination, is seen to describe the instant invention as claimed.